feat(polish): add context safeguards, layered prompts, and output validation

Use redacted cursor neighborhood and pause-aware chunks for more natural polish,
validate protected terms with retry/local fallback, and structure bilingual prompts
for consistency and provider prefix caching.

OSGKeyboardShared/Services/PolishOutputValidator.swift

@@ -0,0 +1,131 @@
+// PolishOutputValidator.swift
+// OSGKeyboard · Shared
+//
+// Deterministic protection for content that must survive an LLM rewrite.
+// High-confidence violations are enforced; noisier heuristics are observed.
+
+import Foundation
+
+public enum PolishViolation: Equatable, Sendable {
+    case missingDictionaryTerms([String])
+    case missingIdentifiers([String])
+    case missingNumbers([String])
+    case lengthOutOfRange(ratio: Double, allowed: ClosedRange<Double>)
+    case languageDrift(inputCJK: Double, outputCJK: Double)
+
+    public var isHard: Bool {
+        switch self {
+        case .missingDictionaryTerms, .missingIdentifiers:
+            return true
+        case .missingNumbers, .lengthOutOfRange, .languageDrift:
+            return false
+        }
+    }
+
+    public var logLabel: String {
+        switch self {
+        case .missingDictionaryTerms(let values): return "dictionary:\(values.count)"
+        case .missingIdentifiers(let values): return "identifier:\(values.count)"
+        case .missingNumbers(let values): return "number:\(values.count)"
+        case .lengthOutOfRange: return "length:1"
+        case .languageDrift: return "language:1"
+        }
+    }
+}
+
+public enum PolishOutputValidator {
+    public static func validate(
+        input: String,
+        output: String,
+        dictionary: PersonalDictionary,
+        lengthRatio: ClosedRange<Double>
+    ) -> [PolishViolation] {
+        var violations: [PolishViolation] = []
+
+        let missingTerms = dictionary.effectiveEntries.compactMap { entry -> String? in
+            let variants = [entry.term] + entry.aliases
+            let appeared = variants.contains {
+                input.range(of: $0, options: [.caseInsensitive, .diacriticInsensitive]) != nil
+            }
+            guard appeared, !output.contains(entry.term) else { return nil }
+            return entry.term
+        }
+        if !missingTerms.isEmpty {
+            violations.append(.missingDictionaryTerms(Array(Set(missingTerms)).sorted()))
+        }
+
+        let missingIdentifiers = protectedIdentifiers(in: input)
+            .filter { !output.contains($0) }
+            .sorted()
+        if !missingIdentifiers.isEmpty {
+            violations.append(.missingIdentifiers(missingIdentifiers))
+        }
+
+        let inputNumbers = matches(#"\d+(?:[.,]\d+)*"#, in: input)
+        let missingNumbers = Array(Set(inputNumbers.filter { !output.contains($0) })).sorted()
+        if !missingNumbers.isEmpty {
+            violations.append(.missingNumbers(missingNumbers))
+        }
+
+        if input.count >= 20 {
+            let ratio = Double(output.count) / Double(max(input.count, 1))
+            if !lengthRatio.contains(ratio) {
+                violations.append(.lengthOutOfRange(ratio: ratio, allowed: lengthRatio))
+            }
+        }
+
+        let inputCJK = TranscriptLanguageDetector.cjkRatio(input)
+        let outputCJK = TranscriptLanguageDetector.cjkRatio(output)
+        if input.count >= 20, abs(inputCJK - outputCJK) >= 0.15 {
+            violations.append(.languageDrift(inputCJK: inputCJK, outputCJK: outputCJK))
+        }
+
+        return violations
+    }
+
+    public static func retryInstruction(
+        for violations: [PolishViolation],
+        useChinese: Bool
+    ) -> String {
+        let protectedValues = violations.flatMap { violation -> [String] in
+            switch violation {
+            case .missingDictionaryTerms(let values), .missingIdentifiers(let values):
+                return values
+            default:
+                return []
+            }
+        }
+        guard !protectedValues.isEmpty else { return "" }
+        let joined = protectedValues.joined(separator: ", ")
+        return useChinese
+            ? "上一次输出遗漏或修改了以下受保护内容：\(joined)。重新处理，并确保它们逐字符原样保留。"
+            : "The previous output omitted or changed protected content: \(joined). Process it again and preserve every item exactly."
+    }
+
+    private static func protectedIdentifiers(in text: String) -> Set<String> {
+        let patterns = [
+            #"https?://[^\s<>"']+"#,
+            #"\b[\w.+-]+@[\w-]+(?:\.[\w-]+)+\b"#,
+            #"(?:^|[\s(])(?:[A-Za-z0-9_.-]+/)+[A-Za-z0-9_.-]+"#,
+            #"\b[A-Za-z][A-Za-z0-9]*_[A-Za-z0-9_]+\b"#,
+            #"\b[A-Za-z]+[a-z0-9][A-Z][A-Za-z0-9]*\b"#,
+        ]
+        var result = Set<String>()
+        for pattern in patterns {
+            for value in matches(pattern, in: text) {
+                result.insert(value.trimmingCharacters(in: .whitespacesAndNewlines.union(
+                    CharacterSet(charactersIn: "(")
+                )))
+            }
+        }
+        return result
+    }
+
+    private static func matches(_ pattern: String, in text: String) -> [String] {
+        guard let regex = try? NSRegularExpression(pattern: pattern) else { return [] }
+        let range = NSRange(text.startIndex..<text.endIndex, in: text)
+        return regex.matches(in: text, range: range).compactMap {
+            Range($0.range, in: text).map { String(text[$0]) }
+        }
+    }
+}